This invention relates to integrated circuit semiconductor devices having voltage invariant capacitor elements, and more particularly, to a method for making such devices.
In certain types of relatively large integrated circuits, it is necessary to provide numerous voltage invariant capacitors in addition to the many transistors used for logic or memory sections. For example, in integrated circuits such as microprocessors or devices used for digital data transmission and communication systems, such as coder-decoder circuits, analog to digital and/or digital to analog converters are formed from capacitor ladders comprised of large numbers of capacitors, all of which must be sized to specifications within close tolerance limits.
Heretofore, in order to provide the necessary capacitor elements in an integrated circuit comprised of many transistors, separate process steps were required to form external capacitor elements. This greatly increased the cost of such integrated circuits. Moreover, it adversely affected the production yield attainable because of process complications and it required integrated circuit chips of greater area. The present invention provides a solution to this problem.